Synthesis of p-n CoO-ZnO Heterojunction for Enhanced Visible-Light Assisted Photodegradation of Methylene Blue

Abstract The synthesis of p-n heterojunction has received much attention in the eradication of organic pollutants from water. In this study, p-n CoO-ZnO heterojunction is reported as an efficient visible-light-driven photocatalyst for degradation of methylene blue. The formation of CoO-ZnO was determined by XRD, XPS, UV-vis DRS, SEM, and EDS analyses. The p-n CoO-ZnO prepared by precipitation method showed an enhanced photocatalytic activity under the irradiation of visible light compared to ZnO. A 100 mg/L methylene blue is degraded almost completely within 2 hours under visible irradiation. The enhanced photocatalytic efficiency is attributed to the synergistic effect of p-n heterojunction that dramatically reduces the recombination of holes and electrons initiated by irradiation. The role played by hydroxyl radicals in photodegradation of methylene blue was determined by photoluminescence emission and fluorescence spectroscopy.